Milk fat fractions from supercritical carbon dioxide (SC-CO 2 ) extraction were compared with commercial melt crystallization (MC) fractions for their physical and chemical properties. The fractions were analyzed for fatty acids, triacylglycerols, cholesterol, total carotenoid content, and volatile compounds. The fractions were also evaluated for solid fat content (SFC) by pulsed nuclear magnetic resonance and thermal profiles by differential scanning calorimeter (DSC). The distribution of fatty acids and triacylglycerols in the fractions depended on the fractionation technique used. SC-CO 2 separated fractions based on molecular weight rather than on melting point, which is the driving force for the MC process. The differences among the fractions were quantified from their SFC and DSC curves. Triacylglycerol profiles by high-performance liquid chromatography showed that the SC-CO 2 fractions were distinctly different from each other and from MC fractions. The SC-CO 2 solid fraction (super stearin) was the most unique. It had a high concentration of long-chain, unsaturated fatty acidcontaining triacylglycerols in a narrow range of high molecular weight, indicating a homogeneity of this fraction that has not been attainable by other techniques. It was also enriched in β-carotene and was devoid of volatile compounds. As compared to liquid MC fractions, the liquid SC-CO 2 fraction had a high concentration of low-melting triacylglycerols and was enriched in volatile compounds. With SC-CO 2 , it is thus possible to simultaneously fractionate and produce a flavor-rich concentrate at no extra processing cost.New food products are being developed at a rapid rate and place high demands for more specialized fats and oils, customized to fit specific applications. Optimal fats, however, cannot always be obtained from nature. Milk fat can be singled out from most other fats in that it has a broad molecular weight range of triacylglycerols (TAG), low (17 wt%), medium (50 wt%) and high (33 wt%), coupled with a pleasing aroma and taste (1). But, when these TAG are viewed as a single entity, they can and do limit the use of milk fat. Price and functionality are important factors that affect usage of milk fat: milk fat has the disadvantage of both high price and limited functionality compared to tailored vegetable fats and oils. Its flavor and its reputation as a natural product are the biggest advantages of milk fat. Moreover, milk fat is required for flavor in certain applications and high-quality foods, e.g., premium cookies and bakery products.Given milk fat's limited functional and nutritional value, its enhanced utilization hinges on providing unique functionality through fractionation. The most common method of milk fat fractionation is by crystallization at different temperatures (melt crystallization, or MC), with or without solvents (2-5). The fractions obtained by dry fractionation, however, show differences in melt characteristics but relatively small variations in chemical composition (1). The use of solvents or surfa...
